netdev - Re: [net-next 1/2] inet_diag: export SO_REUSEADDR and SO

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Message-ID: <20230912162644.60787-1-kuniyu@amazon.com>
Date: Tue, 12 Sep 2023 09:26:44 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <jbaron@...mai.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <netdev@...r.kernel.org>, <pabeni@...hat.com>,
	<kuniyu@...zon.com>
Subject: Re: [net-next 1/2] inet_diag: export SO_REUSEADDR and SO_REUSEPORT sockopts

From: Jason Baron <jbaron@...mai.com>
Date: Tue, 12 Sep 2023 10:31:48 -0400
> Add the ability to monitor SO_REUSEADDR and SO_REUSEPORT for an inet
> socket. These settings are currently readable via getsockopt().
> We have an app that will sometimes fail to bind() and it's helpful to
> understand what other apps are causing the bind() conflict.

If bind() fails with -EADDRINUSE, you can find the conflicting sockets
with just the failing 2-tuple, no ?

Also, BPF iterator and bpf_sk_getsockopt() has the same functionality
with more flexibility.  (See: sol_socket_sockopt() in net/core/filter.c)


> 
> Signed-off-by: Jason Baron <jbaron@...mai.com>
> ---
>  include/linux/inet_diag.h      | 2 ++
>  include/uapi/linux/inet_diag.h | 7 +++++++
>  net/ipv4/inet_diag.c           | 7 +++++++
>  3 files changed, 16 insertions(+)
> 
> diff --git a/include/linux/inet_diag.h b/include/linux/inet_diag.h
> index 84abb30a3fbb..d05a4c26b13d 100644
> --- a/include/linux/inet_diag.h
> +++ b/include/linux/inet_diag.h
> @@ -77,6 +77,8 @@ static inline size_t inet_diag_msg_attrs_size(void)
>  #endif
>  		+ nla_total_size(sizeof(struct inet_diag_sockopt))
>  						     /* INET_DIAG_SOCKOPT */
> +		+ nla_total_size(sizeof(struct inet_diag_reuse))
> +						    /* INET_DIAG_REUSE */
>  		;
>  }
>  int inet_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
> diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h
> index 50655de04c9b..f93eeea1faba 100644
> --- a/include/uapi/linux/inet_diag.h
> +++ b/include/uapi/linux/inet_diag.h
> @@ -161,6 +161,7 @@ enum {
>  	INET_DIAG_SK_BPF_STORAGES,
>  	INET_DIAG_CGROUP_ID,
>  	INET_DIAG_SOCKOPT,
> +	INET_DIAG_REUSE,
>  	__INET_DIAG_MAX,
>  };
>  
> @@ -201,6 +202,12 @@ struct inet_diag_sockopt {
>  		unused:5;
>  };
>  
> +struct inet_diag_reuse {
> +	__u8	reuse:4,
> +		reuseport:1,
> +		unused:3;
> +};
> +
>  /* INET_DIAG_VEGASINFO */
>  
>  struct tcpvegas_info {
> diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
> index e13a84433413..d6ebb1e612fc 100644
> --- a/net/ipv4/inet_diag.c
> +++ b/net/ipv4/inet_diag.c
> @@ -125,6 +125,7 @@ int inet_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
>  			     bool net_admin)
>  {
>  	const struct inet_sock *inet = inet_sk(sk);
> +	struct inet_diag_reuse inet_reuse = {};
>  	struct inet_diag_sockopt inet_sockopt;
>  
>  	if (nla_put_u8(skb, INET_DIAG_SHUTDOWN, sk->sk_shutdown))
> @@ -197,6 +198,12 @@ int inet_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
>  		    &inet_sockopt))
>  		goto errout;
>  
> +	inet_reuse.reuse = sk->sk_reuse;
> +	inet_reuse.reuseport = sk->sk_reuseport;
> +	if (nla_put(skb, INET_DIAG_REUSE, sizeof(inet_reuse),
> +		    &inet_reuse))
> +		goto errout;
> +
>  	return 0;
>  errout:
>  	return 1;
> -- 
> 2.25.1